Perth/WA - Day to Day Weather Talk

Event discussion and analysis for southern Western Australia, including day to day weather.

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Pete
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Tue Dec 27, 2011 7:42 pm

ALBANY:
Remainder of Tuesday: Clear. Moderate to fresh E'ly winds.
Wednesday: Mostly sunny. Moderate E/NE winds, fresh for a period in the morning.
Temperatures Min 15 Max 30
UV Alert: 8:00 am to 4:20 pm, UV Index predicted to reach 12 [Extreme]

Outlook for:
Thursday : Sunny. Min 16 Max 33
Friday : Afternoon thunderstorm risk. Min 18 Max 26
Saturday : Afternoon thunderstorm risk. Min 17 Max 24
Will be a nice end to 2011 if it pulls off. :bringiton:
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crikey
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Tue Dec 27, 2011 8:55 pm

Interesting those top temps forecast before the change Pete.
Just sat down and watched Melbourne weather news ch 9 Melbourne and the weather lady mentioned temps up to 40 deg c for your area and Perth and said we ( in VIC )would get some of those high temps later.in Vic ? :? query?
Not looking that hot from that forecast? Low 30's before change?
Also noted that BOM WATL rain forecast only has up to 5mm for the s/west coast in the coming week to the 3rd of Jan 2012 for your area and Perth.? :?
Image
Rainfall forecast Looks quite underdone looking at the synoptic and WATL wind forecast.
Quite a disturbance of low pressure contours in that area for this change. It is not a simple trough line which might give those lower totals.
Noticed the WATL rainfall ( combined models) sometimes underestimates rainfall but never seen it overshoot the mark yet. I would describe it as a conservative/cautious estimate rainfall model

The synoptic 4 day forecast BOM
http://www.bom.gov.au/australia/charts/4day_col.shtml" onclick="window.open(this.href);return false;
indicating a low ( 1000hpascals) and trough in that area on Thursday the day before your official forecast for the change
and WATL wind map indicates a low forming around carnavaron coastline on Wednesday arvo and slipping south toward Perth on Thursday and the change arriving 4pm on the Thursday
Difference in timing of models l assume. I am slowly cottoning on as to which weather agency uses which models. LOL
Image

Going on the synoptic forecast and WATL wind map for Thursday Friday. and the GFS storm cast map you posted l would say that WATL rainfall forecast is way out for your area.???
Should be 10 mm + min plus 30mm + for high storm potential and quite widespread according to stormcast. From north of perth to the far south down your way
possibly even higher if what happened in Melbourne on christmas day is any indication.
Melbourne got dumped on by storms. GFS stormcast saw the storms but WATL rain forecast didn't compute storm potential and heavy falls
Every chance could be a repeat of something like that over your way in the s/west Thursday night onwards.
The problem with a model like WATL rain forecast is that it doesn't really capture or factor in , the rainfall effect of storms.
How on earth you convey that in a graphical forecast l have no idea. I like the BOM explorer because it has a higher totals tab that lets you view possible higher totals which in real life have been coming to fruition quite regularly lately
A good weather watch hey!! 8-) :P
Pete
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Tue Dec 27, 2011 9:52 pm

crikey wrote:Interesting those top temps forecast before the change Pete.
Just sat down and watched Melbourne weather news ch 9 Melbourne and the weather lady mentioned temps up to 40 deg c for your area and Perth and said we ( in VIC )would get some of those high temps later.in Vic ? :? query?
Yeah I think the heat will continue to move into Vic by the beginning of 2012, the GFS models show the "heat line" as I like to call it, extending as far south as northern Vic, I think you could see temps there of 35C+ next week. Maybe as high as 40C or more?
crikey wrote:Not looking that hot from that forecast? Low 30's before change?
I think the BoM is maybe underestimating the heat? Particularly for Thursday down here, strong N'lies associated with the low and trough, I'm thinking temps of near 35C here on Thursday. For the rest of the state, I reckon they're pretty much spot on, northern inland parts could easily reach 40C+ before the change. Just uncertain about the timing of the trough at this stage, it is a good few days out. Also an upper level trough expected to approach Friday and help enhance thunderstorm development in the southern and eastern parts. Watching this one closely, haven't seen a decent flang fest for ages.

Not sure about rainfall totals. GFS accumulated precipitation is all over the place. Going for areas of 75mm+ in the southern central agricultural districts. I think if we get a storm we'll see at least 10mm from one. There's a lot of upper level moisture coming in off the Indian Ocean from the west/northwest, I think maybe another scenario like a few weeks back is on the cards again? Severe thunderstorms with flashflooding, inland its possible at this stage. Yep, keeping an eye on this closely. :)

Pete
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crikey
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Thu Dec 29, 2011 11:34 pm

Howdy pete from victoria the home of some 'crackin thunderstorms' Lately anyway.LOL
Noticed you were right about the higher temps with the northerlies today. Albany airport making 35 deg c today at 12.30pm spot on !!
Then a nice cool wind change
2 deg c above the BOM forecast
Perth making 37. deg c at about the same time
I am still feeling bemused re the WATL rainfall forecast for the s/west . Still indicating only a couple of mm and yet BSCH stormcast indicating what could be some strong storms in the s/west corner tomorrow friday from 4pm to 1pm
Image
Maximum temp expected tomorrow.36 to 39 deg c in the areas marked by stormcast for posible severe storms
Noticed your max is only 26 deg C.
The WATL wind map indicating a well formed low in the s/west corner . Your area on friday arvo.
Your area over Albany showing some nice wind convergence on the coast.near Albany! N/easterlies from the low converging with cool moist onshore south /south westerlies AND Easterlies, in-feeding into the low from the southern ocean. Looking good.
I have Marked it for an interesting weather watch tomorrow arvo/ evening..
Stormcast has all the action north of you but if WATL wind flow is correct could be further south. Cooler temps may temper the intensity though.?
Anyway .. Lets see.
The BOM synoptic showing that low in s/west corner on friday morning a little earlier than WATL wind forecast map
still finding it hard to believe you will only get 1 -5mm?
Maybe not enough moisture or low dew points or something?
Anyway love the set up that WATL wind is portraying for down your way. tomorrow arvo. 8-)
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daviescr
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Fri Dec 30, 2011 7:23 am

Yes it does look interesting Crikey - certainly got my attention - i'm just about to hop on a plane to Perth for a few hours of urgent work, aiming to leave at 5pm - will certainly be an interesting journey home if GFS is right :o :o
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crikey
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Fri Dec 30, 2011 10:43 pm

Howdy .Daviecr. Just thinking about your plane flight. Just saw stormtracker lots of activity in the southern part of WA atm.and wondered how air planes deal with line of thunderstorms. Do they go around the long way( divert) or do they fly above)
These storms not putting out much rain so thought maybe not very tall ( high) into the troposphere? I think some call them mid level storms?
Did you get a bumpy ride or did they fly well above them? Did you see the tops of the storm clouds?

Storm line approaching the south west coastline. Not severe. I know where pete is..Click click! What type of storm clouds pete?. I am not up with the classification jargon.They are not putting out much rain. Probably just how storm chaser like them hey! Clear sky and a few booming cells.. 8-)
Only made it to about 22 deg c in Albany today the cool westerlies were in this morning. Some mid/upper? cloud pushing south and some ground cool southerlies pushing north. Looks like a convergence line atm. ?
Pete
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Sat Dec 31, 2011 1:03 am

Ha, yeah had a bit of a light show tonight. Didn't get to see the type of storm clouds, it was too dark. :P The lightning was all over the place; difficult to capture. Yeah, I think there's a convergence line developing, its been cool and cloudy all day, yet now the low cloud has cleared and the wind has switched W/NW. :?
So might get some more action over night. Oh and it got to 36.5 yesterday at 12:34pm. That was the official max.
Pete
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Sat Dec 31, 2011 1:26 pm

Yes, I think we had a convergence line go over us last night. That would of been the only thing responsible for the thunderstorms. Looking at yesterday's skew-t sounding there was quite a strong inversion layer near the surface, the lapse rates were quite shallow, and instability and CAPE were very marginal. I would say it was too to the high amount of moisture near the surface that released latent heat, that with the forced lifting in the mid-levels caused by the upper level trough, caused brief high-based low-topped thunderstorms to happen. Strange thing is, the lightning was nearly overhead, yet there was no thunder and the airport reported no lightning in their obs last night, so it must of been quite isolated.

Looking at today, I'd say its all over near the coasts, that trough is moving east, so any development today will be well inland. Just have to wait until around lunch time for things to explode before the chasers head out again. Quite a few people from the WAWG forum chased yesterday, I don't know if anyone saw the photos on FB? There's photos here: http://waweathergroup.com/forum/viewtop ... &start=600" onclick="window.open(this.href);return false; Go to page 31. :)

In regards to the next event, it looks like we'll see a similar pattern, except the high pressure system will be further north and more circular shaped, allowing N/NE winds across the state instead of E'lies like we've been having with all our recent storm events. So heating should be better with this one. Trough looks deeper at this stage, and again and embedded low to the north of Perth, but too far out too tell what level the steering winds will be.

GFS has this at a bit of a rain event with 25mm-50mm forecast for the next week. Storm potential looks good. Hoping we'll get a nice show to kick of 2012. Happy New Year everyone. Drive safe, drink lots and eat well. Have fun. :)

Pete
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crikey
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Sat Dec 31, 2011 10:06 pm

WZ have written a news article and reckon potential for severe storms tonight.Pete Noticed them cranking up!
When l looked at the national loop and radar wind surface direction , the set up looked identical to last night.
A small partial surface low far south west corner near you and cloud pushing down south toward you. In fact the storms are pretty much in the same place as last night.
Had a look at ACCESS wind streams for the upper levels
http://www.bom.gov.au/australia/charts/ ... u&model=CG" onclick="window.open(this.href);return false;
and learnt tonight that the cloud pushing south down toward you is following the 200 , 500 and 700 hpascal wind stream which is united in traveling toward the south and coast .hence the cloud on national loop following upper and mid wind stream
Now at the surface there is a small surface low and cold moist southerlies streaming inland almost the opposite way . So the convergence is at about 850 hpascals lower mid level ( l assume)
So mild rotating surface air mass with fair uplift being sheared across at the mid levels.
Any way that's how l envisage the air streams and instability. As for how the thunderstorms start as a result of that l have no idea?? One day l read about it LOL
Anyway looks like plenty for stormchasers tonight. Hope they don't drink and drive!!
Noticed that last night some mountain to the east had 112mm. Couldn't help thinking that , that was all that was needed for some heav7y rain from those storms. They needed more uplift for rain..by the looks. You did mention the lifted index was pretty ordinary. Because the dew points around your area were excellent in the 18 deg c range
So l learnt a great deal from that weather watch. Thanks for the help and commentary pete. Appreciated
Happy new year to you and your family. Looks like you have your own fireworks show there tonight. 8-)

Wondering why the storms were more severe tonight . Was the LI and CAPE etc better tonight ?
------------------------------------------------------------------------------------------------------------------
IDW28201
Australian Government Bureau of Meteorology
Western Australia

TOP PRIORITY FOR IMMEDIATE BROADCAST
SEVERE THUNDERSTORM WARNING

Large Hail, Damaging Winds and Heavy Rainfall
For people in southern inland parts of WA bounded by Northam to Katanning to
Bremer Bay to Israelite Bay to Salmon Gums to Northam including the town of
Esperance.

Issued at 6:25 pm on Saturday 31 December 2011

WEATHER SITUATION

People are advised that there is a risk of severe thunderstorms during Saturday
evening. Storms may be accompanied by VERY HEAVY RAINFALL conducive to FLASH
FLOODING and LARGE HAIL and DAMAGING WINDS that could result in DAMAGE TO HOMES
AND PROPERTY IN LOCALISED AREAS.

The overall weather pattern is not unusual for this time of year, but these
thunderstorms may
produce severe weather in localised areas.
Pete
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Sun Jan 01, 2012 11:48 am

Yeah the storms fired up again last night, a lot more widespread in eastern part, which I think was due to the mid-level trough being closer to the surface trough and there were also two surface lows present, one on the trough and one to the east of the trough and there was also upper level circulation to the north of Perth, that lifting caused the storms in the Great Southern. The storms in the Great Southern, although severe, were disorganised and short-lived, they became out-flow dominated quite quickly and lost all their features. Hence we just got moderate rainfall from non-lightning active CB's. The ones to the east however had the heat, favourable surface winds as well as upper winds, although instability wasn't to flash, there must have been an incredible amount of forced lifting.
So fizzer for Perth and the southwest, but eastern parts copped it bad. Moving onto 2012.

This set-up looks a bit more organised with a stronger high providing gusty E/NE winds on Wednesday which will allow for good surface heating, although not strong, so thunderstorms may fire up late in the day near southern parts. Thursday looks a lot better, the low and trough deepens and extends south throughout the state, so thunderstorms should become more widespread across southern and eastern parts. At this stage moisture and heat looks awesome, Perth going for 38C on Thursday, Albany at 29C, with dew points across the southern half predicted to reach 20C+! So we have heat, an abundance of moisture, favourable shear and forced lifting. Everything looks great for a nice few days of wild storms producing plenty of carnage. 8-) Well, it is 2012 after all. :P
Pete
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Sun Jan 01, 2012 8:29 pm

My first post for the new year, so its a good one. :)
Image
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crikey
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Tue Jan 03, 2012 11:23 am

Hope you are enjoying your holidays Pete. Year 12 this year?
Re your WZ forecast for Albany. Noticed BOM forecast rainfall has you for 5-10mm for the 3rd Jan to the 6thJan
http://www.bom.gov.au/jsp/watl/rainfall/pme.jsp" onclick="window.open(this.href);return false;
However if you calculate the higher end of the range presented by weatherzone from your post above , you might say 90% chance of up to 30mm for the same time period plus another 10mm for the 7th Jan. Higher range up to 40mm for this event
WATL wind forecast indicating a low developing on the west coast, north of Perth and then rolling down south hugging the coastline and dropping just south of you.
http://www.bom.gov.au/jsp/watl/wind/index.jsp" onclick="window.open(this.href);return false;
So looks good for chances of rain for Perth and the s/west.
This same low is forecast by WATL wind ( EC) to traverse s/east into the southern ocean and intensify 'big time'. By next sunday it is just massive, as a sub polar low .
Actually why l was wanting to post this morning was that l saw on metoffice world sat pic tropical cyclone Benilde in the Indian ocean looking to integrate into a passing trough and closely following behind another heat low/TS.
http://www.metoffice.gov.uk/weather/satellite/" onclick="window.open(this.href);return false;
http://www.usno.navy.mil/JTWC/" onclick="window.open(this.href);return false;
The moisture laden remnants of this cyclone should integrate into this trough .
Should be a good watch as the trough approaches WA. 8-)
When do you think this trough in Indian ocean will approach WA.?
Image
Ken mentioned in the wet S/east thread that there was a wet signal upcoming for east Australia. Figuring that this trough could be it? May even involve further moisture infeeds from north as well but that's just conjecture on my part.
EDIT
Gee a nice healthy cold pool pushing toward you this morning on the national loop radar
Possibly jumper weather?
12.2 deg C at 4.00am..LOL
http://www.bom.gov.au/products/national ... loop.shtml" onclick="window.open(this.href);return false;
Pete
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Tue Jan 03, 2012 12:31 pm

Ah, my holidays are boring. Not enough storms. :P And yes, year 12 this year, I'm doing a lot of maths and physics so they are letting me take longer to do it. :) Then I'm off to uni, hopefully to do a Bsc in atmospheric science.
Yeah I think GFS is underestimating the rainfall outlook, going for just 25mm for Albany in the next seven days. :? http://forecasts.bsch.au.com/apf.html?r ... 2012010218" onclick="window.open(this.href);return false;
I'm thinking more like 30 - 60mm over the next seven days? These thunderstorms have the potential to become severe on Thursday, and flash flooding looks the main risk with these storms at this stage.
And with that low sitting just northwest of us on Friday morning - things could get very interesting. http://www.bom.gov.au/australia/charts/ ... ndex.shtml" onclick="window.open(this.href);return false;
From what I've looked at on the WATL forecast charts, the low and trough should move east between 4am and 10am. So we could have a nice light show overnight.
Yeah watching this cyclone quite closely, its taking a southerly track now and appears to be weakening - latest satellite imagery from that area showed it not looking too organised. WZ synoptic has a low and cold front moving up behind this system during Saturday, I'm thinking that could be very interesting. Its releasing a great amount of moisture into the Indian Ocean, also there's quite a decent cold pool associated with this system considering its January. 500mb temps forecast to be -20C? Looks like Saturday could be cold and windy. Be quite a change from Thursday, we're going for 30 degrees. So more jumper weather coming up.

I'm not familiar with the weather set-ups you guys get over east, but yeah that low is looking nasty on the models. Some have it tracking southeast and missing SE Australia completely, but that's way too far out to predict with any accuracy, so I'm not going to speculate on that. Anyway looks like you've got some cool nights ahead, 9 degrees for Thursday and Friday? Far out.

Pete :)
Pete
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Wed Jan 04, 2012 1:28 pm

Insane storms in Perth last night, check the forum for photos. :) http://waweathergroup.com/forum/viewtop ... &start=240" onclick="window.open(this.href);return false; Hope I ain't spamming.
Convection going up here already despite the massive inversion on the sounding and the fact that its only 21 degrees. Going to be one hell of a day.
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daviescr
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Wed Jan 04, 2012 1:51 pm

Not spamming at all Pete, more than happy to share the action :) I saw Marie Frietag's images on facebook this morning - absolutely stunning!

Hope you get some crackers down your way in Albany - certainly looking that way on the tracker :lighting: :lighting:
Pete
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Wed Jan 04, 2012 6:22 pm

Thunder and LIGHTNING! :D
Pete
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Thu Jan 05, 2012 2:52 pm

TOP PRIORITY FOR IMMEDIATE BROADCAST
SEVERE THUNDERSTORM WARNING
for Damaging Winds, Large Hail and Heavy Rainfall
For people in parts of WA in an area bounded by Walpole to Narrogin to Mount
Jackson to Kalgoorlie to Norseman to Esperance and along the south coast to
Walpole. This includes people in, near or between the towns of Kalgoorlie,
Albany and Esperance.
Issued at 9:50 am on Thursday 5 January 2012

WEATHER SITUATION

People are advised that there is a risk of severe thunderstorms during Thursday
afternoon and evening.
Storms may be accompanied by VERY HEAVY RAINFALL conducive to FLASH FLOODING,
LARGE HAIL and DAMAGING WINDS that could result in DAMAGE TO HOMES AND PROPERTY.

The overall weather pattern is not unusual for this time of year, but these
thunderstorms may
produce severe weather in localised areas.

WHAT TO DO
FESA State Emergency Service [SES] advises people to secure loose items, move
vehicles under cover and stay inside away from windows. If there is lightning
unplug electrical appliances and avoid using landline telephones. If caught
outside find shelter away from trees, powerlines, storm water drains and
streams. If driving through heavy rain slow down and turn your lights on or if
visibility becomes low pull over and park until it passes. For SES assistance
call 132 500. For more safety tips visit http://www.fesa.wa.gov.au" onclick="window.open(this.href);return false;

The next warning will be issued by 1:00pm WST Thursday.

This warning is also available through TV and Radio broadcasts; the Bureau's
website at http://www.bom.gov.au" onclick="window.open(this.href);return false; or call 1300 659 213.
Pete
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Thu Jan 05, 2012 2:52 pm

Epic thunderstorm went through this morning, photos and videos to come. :)
Pete
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Fri Jan 06, 2012 12:30 pm

Well, that's all the excitement over till the next event. Next event looks like the 12th maybe. Some models have a possible tropical cyclone developing off the Pilbara mid-next week, at the same time a deep surface trough develops. Too far out to tell what's gonna happen. Interesting weather tomorrow, 850 temps are out 3-4 degrees so we may see some quite decent showers tomorrow. Pressure gradient is pretty tight with that deep low developing in the Southern Ocean. Winds are already doing 61km/h gusts here in Albany.
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crikey
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Fri Jan 06, 2012 11:50 pm

Thanks for all that info and updates Pete. Had a look through the WA forum from the link you provided. It certainly wAS EVENTFUL!!
An excellent coverage of the event from WAforum. Enjoyed :P
WATL wind is showing that low/TS up in the N/west and has it shifting down toward carnavon area before weakening into nothing.
My current evaluation/opinion of WATL wind , for its forecast of TC's in the tropical region is currently poor.
WATL has not done very well up north but pretty pleased with how it performs in mid-latitudes.
Last time l compared, ACCESS global did better than WATL for TC development forecast.
from perth news Now from a link in WA forum
And the rest of the 38 photos published in the gallery for this storm are found here
http://www.perthnow.com.au/gallery-e6fr ... 744?page=1" onclick="window.open(this.href);return false;
Image
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